Commutator control of booster rotary converters



Sgpt. 14 1926.

F. T. HAGUE COMIUTATOR CONTROL OF BOOSTER ROTARY CONVERTERS Filed March 10, 1923 I INVENTOR Floyd T Hague.

WITN ESSES: Q 0K.

ATTORNEY Patented Sept. 14, 1926.

UNITED STATES PATENT OFFICE.

FLOYD T. HAGUE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

COMMUTATOR CONTROL OF BOOSTER ROTARY CONVERTERS.

Application filed March 10, 1923.

My invention relates, in general, to methods of, and means for, controlling the com-- mutation of direct-current machines, with particular relation to synchronous booster converters.

The development of large -cycle Edison systems, or three-wire systems fed by rotary converters from a 25-cycle supply line, has necessitated the use of two or more non-interconnected alternating current power sup ly systems for the supply of a plurality o converters which feed into a common direct-current network. The introduction of (SO-cycle Edison systems presents a second case of parallel direct-current operation with independent alternating-current power supplies. A fundamental requirement of safe operation of the paralleled converters has proven to be the 20 maintenance of the correct commutating pole strength under normal and emergency conditions of operation.

- For a number of years .ast, booster rotary converters have been esigned and utilized in commercial systems having commutation control mechanism meeting all of the requirements of direct converter operation. but being deficient on inverted converter operation, as when the voltage suddenly drops in one of the independent alternating-current supply systems. It is my belief that the difiiculty with prior control systems has been either that the auxiliary commutating field has been merely reduced to zero ,upon inverted converter operation, or. if the auxiliary commutating field has been reversed at all prior to my present invention, this feature has not been utilized in the combinations necessary to produce correct commutation control for booster rotary converters, or the action has been entirely too slow to prevent the burning ofi of the brushes or commutator during emergency conditions when the converter is suddenly operated in inverted condition.

The principal object of my invention, therefore, is to devise a method of. and means for, properly reversing the auxiliary commutating field upon the occurrence o1 inverted converter operation.

Another object of my invention is to provide a double-acting torque motor which is capable of moving a reversing rheostat in either direction from its neutral position.

Serial No. 624,150.

A more specific object of my invention is to provide means for controlling an auxiliary shunt commutating winding on a rotary converter in accordance with the setting of the field rheostat of a boosterassociated therewith, and, at the same time, correcting the exciting current of the auxihary commutating winding in accordance with the direction and magnitude of the load current of the converter.

WVith the above: and other objects in view, my invention consists in the methods and apparatus described in the following speci fication, particularly pointed out in the sub joined claims, and illustrated in the accom-= panying drawing.

In general, my invention is an improvement upon the system and apparatus aescribed in an article entitled Synchronous booster rotary converters, by J. L. McK. Yardley, appearing on page 267 et seq, of the Electric Journal for 1914, and also de= scribed and claimed in Patent No. 1,392,076, granted September 27, 1921, to F. D. Newbury and H. D. J ame's, and assigned to the Westinghouse Electric and Manufacturing Company. In order to avoid unnecessary repetition, in the present application, of what is already known, a general reference is hereby made to the above entitled article and patent for a further understanding of the prior-art apparatus and practice upon which my present improvements are based.

The three figures of the accompanying drawing are diagrammatic views of circuits and apparatus embodying my invention in three different forms, the preferred form be ing indicated in Fig. 2.

In Figure 1 is shown a booster rotary' converter system comprising a three-wire direct-current network 4, having a positive conductor 5. a negative conductor 6 and a neutral conductor 7, supplied from a rotary converter 8, which is, in turn, energized through a mechanically and electrically connected booster 9, from an alternating current supply system 10. The converter 8 is provided with main poles 11 and interpoles 12. the main poles 11 being energized by a main shunt winding 13 associated with a shunt field rheostat 14, and the inter-poles 12 being energized, in part, by a series com mutating winding 15 which is adjusted to connected across the nositive and neg) conductors and (3 ot the direct system.

At auv given lozul-currcnt carried h tl converter 8. it has been recognize-fl. in times past. that the autilliarv commutatinn winding' 16 should he Xcited by a :urrent vhich *ai'ies in direction and magnitude in accordance with the booster voltage the ratio le tween the RHX llZ lY connnutatinp; current and the booster voltage preteral l in-r'a'earing as the booster is adjusted from maximum huck to maxin'ium boost.

I have. thereto 'e. shown. in rheostat 19. which is elect-ricallv connected in series with the auxiliarv coinniutating winding 16. and which is mechanically connected to the helm rheostat 18 ot the booster bv means of a common shaft 20. the resistor 19 being so adjusted that the resi .nce is gradually cut out the hooster enc'tation is increased in either direction from zero, and the steps of the resistors beingso chosen that the ratio betveen the auxiliary commutating winding current and the booster voltage increases the booster is adj d from maximum buck to maximum boost. A

Fig. 1. a

suitable reversing switch 21 is also provided which should be ope ated whenever the hanclle ot the booster regulating rheostat 18 is moved through its neutral position.

In order to provide a control svstem which shall meet the requirements of sudden inverted converter operation, I have provided a double-acting; torque motor comprising an armature member 23 mounted upon a shaft 2% and energized from the di ect-current mains through a small adjusting resistor 25. The torque motor 22 is also pr vided with field winding 26 which connected across the series cominutatine' winding in order to be energiz ,d in accordance with the direct current supplied by the converter.

Mounted upon the shaft 2 lot the torque motor is a movable arm 27 or" a reversing; rheostat- 28 which is connected across the positive and negative conductors arl 6 oi" the direct-current mains. The torque motor 22 and rheostat 28 are biased toward the neutral position 01" the rhcostat lrv means of a pair of oppositelv-aetin springs mounted upon the shaft 24. V

The circuit comprising: the auxiliarv (our mutatingwinding 16. the rovers 1:1 switch 21 m d the variable resistor 10 is serially connected, through a small adjusting resistor 30, between the movable arni 27 ot the rheo 2S and the neural conductor 'i oi: the .-re -t-cirrrent mains.

In 2 I shown the par ilar Form of apparatus which has heen developed and placed in success'lul service. In the modi- U" Cl 1' X ir' l l iinz-x' r 1 nation ion. in L 1. ellt. 1.) er the reversing switch 21 is avoided by replacthe var able resistor 19 hv a reversing resistor 331, which changes sign at he same t me doe a booster liel l voltage derived tron: the l a .9.. the. ther connections ren'iainin as lfl B151. 1. In Fig. 2.

hvc her-n replaced. tor purposes 0 -r 1 o a biasingweight arm to indicate l that my invent ioi not necessarilv restricted to the cmplovment o't any particular form oi? liiiasing means.

In 3 is shown a somewhat ll oi iiied also. the

construction comprising: a rheostat 28 en- 'i d across the pos ive and negative con- 5 and ii end having; its midpoint 33 s movable arm 27 coon respecto the tr urinals ot a reversing: rheoiniilar it) the reversing rheostat 31 The rheostats 2S and Bl are 1 i. respectively. on the sha'i'ts 2i; and he torque motor and the booster r ieostat 18. The reversing rlieostat 31 is provided with two cont: ct arms ll which are connected. througha small regulating: resistor to the auxiliary coniniuta-ing winding 16 ot the converter.

The operation of my a pparatus will be apparentn the :loreg'oing description. in particular. it in noted that; when the direct-curren in the series commutator winding 15 rev -.s. under c'i nditions of inverted converter ODQl'Zi ElO/il. the motor 22 is reversed an: n h arm 2? of the rever... rhe at is quiz i moved to the opposite side ot neutral point. wl reb the voltage applied to the exciting i 16 is reversed. In the foreeoingr specification ant.

t pie o the torque appended chums I l we used the clip reversing rhecstr-t to designate :1 rl which applies a zero g x) trolled circuit when the rh, rm

api e 'ati ve Jicn. its ii neutral v tho relfierence to three modifications, and in accordance with theories of operation which are, alt-present, believed to be proper, it is obvious that various substitutions and alterations may he adoptedwithout departing from the broad principles of my invention. I desire, therefore, that the following claims shall be given the broadest construdion consistent with their terminology when con sidered in the light of the prior art.

I claim .as my invention 1. The con'ibination with a synchronous booster rotary converterof the interpole type rovided with a series-type commutating eld winding designed to produce the proper commutating field under conditions of zero buck or boost and further provided with an auxiliary commutating field winding, of means for exciting said last-mentioned winding, in direction and in magnitude, in acoordance with the excitation of the booster machine, means for further regulating the excitation of said auxiliary field winding in accordance with the direction and magnitude of the load current of the converter, said last-mentioned means comprising a reversing rheostat in circuit with said auxiliary field winding, means for biasing said reversing rheostat to neutral position, and a variable-torque means responsive to the dimotion and magnitude of said load current for actuating said reversing rheostat in either direction from its neutral position.

2; The combination "with a rotary converter provided with cross-field windings, of a booster electrically associated therewith and provided with field windings, means for supplying a component of excitation to said crossfield windings in accordance with thedine'ct current of the converter, auxilary means tor adjusting both the strength and direction of the excitation of said lmooster field windings and for simultaneous ly and similarly supplying a component of excitation to said cross-field windings, and quickncting means responsive to both the direction and the magnitude of the load current of the converter for supplying a variable, reversible electro-motive force in series with said cross-field windings and with their associated auxiliary means.

3. The combination with a rotary converter provided with cross-field windings, of a booster electrically associated therewith and provided with field windings, means for supplying a component of excitation to said cross-field winding-s in accordance with the direct current of the converter, auxiliary means for adjusting both the strength and direction of the excitation of said booster fielsd windings and for simultaneously and similarly supplying a component of excitation to said crossfield windings, torqueindi-cating means responsive to the product of the boosted "voltage and the load. current of said converter, and means responsive to said torque indicating means for supplying a variable, reversible electromotivc force in .series with said cross-field windings and with their associated auxiliary means.

4. The combination with a rotary converter provided with cross-field winding-rs, of a booster electrically associated therewith and provided with field windings, main means for exciting said cross'field windings in accordance with the load current of the converter, auxiliary means for adjusting both the strength and direction oi the excitation of said booster field windings and for simultaneously supplying a component of cxcitation to said cross-field windings, said auxiliary means operating in such manner that said component of excitation opposes said main cross-field excitation during boosting conditions and assists the same during bucking conditions, and operating also in such manner that the ratio between said componentof excitation and said booster field e2:- citation increases as said auxiliary means is adjusted from maximum buck to maximum boost, :and quicleacting electro-responsive means for reversing the voltage applied to said cross-field windings during inverted operation of the converter.

The combination with a rotary converter provided with cross-field windings, ot' a booster electrically associated therewith and provided with field windings, means for si'ipplying a component of excitation to said cross-field windings in accordance with thedirect current of the converter, auxiliary means for adjusting both the strength and direction of the excitation of said booster field windings and for simul' taneously and similarly supplying a component of excitation to said cross-field windings, and quick-acting electro-responsive means ior reversing the voltage applied to said cross-field windings through their associated auxiliary means during inverted operation of the converter.

6. The method of improving the com mutation of a synchronous booster rotary converter of the class described, which consists in maintaining a comn'iutating field having a component proportional to the load current of the converter, maintaining an additional component of commutating field which varies in direction and inmagnitude in accordance with the adjustments of the voltage oi? the booster, and effecting a reversal of said commutating field upon inverted operation of the converter.

7. The method of improving the commutation of a synchronous booster rotary converter of the class described, which cousists in maintaining a commutating field. having a component proportional to the load current of the converter, maintaining an additional component of commut-ating field which varies in direction and in magnitude in accordance with the adjustments to the voltage of the booster, causing the ratio between said last-mentioned component and said booster voltage to increase as said booster is adjusted 'trom maximum buck to maximum boost and ellecting a reversal of said conunutating field upon inverted operation ot the converter.

8. The method of improving the commutation of a synchroimus booster rotary converter. which consists in maintaining a commutating field having a component which varies in direction and magnitude in accord ance with the adjustments of the voltage ot the booster, and varyingsaid component in direction and magnitude in accordance with the load current of said converter.

9. The method of in'iproving the com muttion ot a synchronous booster rotary converter, which consists in maintaining a commutatin'g field having a component which varies in direction and magnitude in accordance with the adjustments of the voltage or the booster, causing the ratio between said component and said booster voltage to increase as said booster is adjusted from maximum bucl: to maximum boost, and varying said component in direction and magnitude in accordance with the load current of said converter.

10. lhe combination with a rotary converter of an alternating-current booster elect really and mechanically associated therewith, means for compensating for variations in the armature reaction under the brushes of the converter occasioned by the booster, and additional means fo reversing the eii'ect of said first-mentioned means up on inverteijl operation of said converter.

ll. The combination with a plurality of urine-electric machines mechanically cour electrically connected in series circuit relation, of means operatively associated with both machines tor assisting in rc lating the voltage and securing good .nutating conditions on one of said machines. and additional means responsive to the. magnitude and the direction of the elec trical power supplied to or by said lastiuent oned machine for varying the corrective eti'ect at said first ientioned means on said commntating co: ions.

12.51 direct-current machine having a shunt commutating field winding. a reversing rhecstat Ii circuit with said winding, means for biasing said rheostat to neutral position, and a variable torque means responsive to both the direction and magnitude of the load current for actuating said reversing rheostat in either direction from its neutral position.

121A, (lirect-cm'rent machine having a shunt commutating field winding, a revers in rhcostat in circuit with said winding,

means for biasing said rheostat to neutral position, and a variable torque means responsive to both the direction and magnitude of the product ot the voltage and current for actuating said reversing rheostat in either direction from its neutral position.

it. The combination with a three-wire, direct-current system comprising positive, negative and neutral conductors, and a direct-current machine associated therewith and having an exciting field winding, a main series connnutating winding and an auxiliarv commutating winding, of a direct-current torque motor having field and armature windings one of which is connected across said series commutating winding and the other of which is connected across said positive and negative conductors, a rheostat connected across said positive and negative conductors, said rheostat having a relatively movable contact arm, a mechanical connection between said rheostat and said torque motor, biasing means tending to maintain said contact arm in mid-position, an auxiliary variable resistor, and a circuit including said auxiliary eommutating winding and said auxiliary variable resistor, said circuit being serially connected between said contact arm and said neutral conductor.

15. In combination. a three-wire, direct current system comprising positive, negative and neutral conductors, a rotary converter associated therewith and having an exciting field winding, a main series connnutating winding and an auxiliary commutating winding, a booster mechanically and electrically connected to said rotary converter and having an exciting field winding, :1 direct-current torque motor ha *ing field and armature windings one of which is connected cross said serl commutating winding and the other of which is connected across said positive and negative conductors, a rheostat connected across said positive and negative conductors, said rheostat having a relatively movable contact arm, a mechanical connection between said rheostat and said torque motor, biasing means tending to maintain said contact arm in n'iid-position, an auxiliary reversing rheostat, means for variably exciting said booster field winding, means tor adjusting said auxiliary rheostat in accordance with the booster adjustment, and a circuit including said auxiliary connnutating winding and said auxiliary reversing rheostat, said circuit being serially connected between said contact arm and said neutral conductor.

16. In combination. a direct-current circuit comprising positive and negative conductors, a rotary converter associated therewith and having an exciting field winding, a main series commutating winding and an auxiliary commutating winding. a booster mechanically and electrically connected to said rotary converter and having an exciting field winding, a direct-current torque motor having field and armature windings one of which is connected across said series commutating winding and the other of which is energized from said positive and negative conductors, a rheostat connected across said positive and ne ative conductors, said rheostat having a re atively movable contact arm, a mechanical connection between said rheostat and said torque motor, biasing means tending to maintain said contact arm in midposition, an auxiliary reversing rheostat, means for variably exciting said booster field winding, means for adjusting said auxiliary rheostat in accordance with the booster adjustment, means for reversibly energizing said reversing rheostat from said movable arm and a point of substantially zero poten tial relatively to said positive and negative conductors and means for reversibly energizing said auxiliary commutating winding from saidreversing rheostat.

In testimony whereof, I have hereunto subscribed my name this 6th day of March 1923.

FLOYD T. HAGUE. 

